Booting Windows 10 from external media
27.06.2020
Booting Windows 10 from external media on a new MacBook Pro isn't as easy as it used to be, but IT CAN BE DONE! :-)
The Mac will only boot via EFI, hence the Windows 10 disk has to be formatted
as GPT
. When looking
for a tool to convert a Windows installation from
MBR
to GPT I stumbled
across several dubious looking 3rd party tools at first. After a while
I realized that Windows 10 already ships with a tool that does the job -
MBR2GPT.exe
. This took a while but did work.
However, the Mac won't boot Windows directly - it has to be blessed (!) first.
In order to bless the Windows installation you have to boot the Mac into Recovery (!), then open a terminal and cast the secret spells:
csrutil disable
bless -mount /Volumes/BOOTCAMP -setBoot
csrutil enable
Not too obvious I guess.